Photosensitive resin compositions for printing plates, resists and the like, which are developable with water, are known in the art.
The resin compositions are generally prepared by dissolving a polyvinyl alcohol in water and then admixing a monomer and a photopolymerization initiator. The compositions are applied on a suitable substrate and then water is evaporated to obtain a photosensitive resin plate for printing. The photosensitive resin compositions employ water as a solvent which must be removed from the composition. The removal of water requires a large scale apparatus and takes time.
The photosensitive resin compositions contain oxygen, called "dissolved oxygen", in a small amount, but the oxygen has a function of polymerization inhibition which often provides poor reproducibility of thin lines. In order to obviate the problem, the compositions are preliminarily exposed to light to consume the dissolved oxygen, before the main exposure. The preliminary exposure to the light, however, makes the process complicated. A photosensitive resin composition which does not need such preliminary exposure is therefore desired.
Also, the cured resin composition is required to have suitable hardness. If the cured composition is too hard, it is fragile and often broken or cracked. If it is not hard, the composition has poor printing properties. The hardness can be controlled by lowering the saponification degree of the polyvinyl alcohol, but the low saponification degree adversely affects water solubility and reduces the water developability.